OBJECTIVES: 1) Investigation of the enzyme defect in a patient with hypermethioninemia, mental retardation and hepatomegaly. 2) Studies of biochemical abnormalities in the tissues from a patient with glutaric acidemia. 3) Continued evaluation of the offspring of phenylketonuric mothers in terms of the effectiveness of dietotherapy during pregnancy, and the relationship between the blood phenylalanine level of the mother and the intellectual achievement of her offspring. 4) Biochemical and clinical evaluation of dietary and megavitamin treatment for patients with various metabolic disorders of amino acids and organic acids.